Tuning Lewis Acidity of Metal–Organic Frameworks via Perfluorination of Bridging Ligands: Spectroscopic, Theoretical, and Catalytic Studies
摘要:
The Lewis acidity of metal-organic frameworks (MOFs) has attracted much research interest in recent years. We report here the development of two quantitative methods for determining the Lewis acidity of MOFs-based on electron paramagnetic resonance (EPR) spectroscopy of MOF-bound superoxide (O-2(center dot-)) and fluorescence spectroscopy of MOF-bound N-methylacridone (NMA)-and a simple strategy that significantly enhances MOF Lewis acidity through ligand perfluorination. Two new perfluorinated MOFs, Zr-6-fBDC and Zr-6-fBPDC, where H(2)fBDC is 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylic acid and H(2)fBPD C is 2,2',3,3',5,5',6,6'-octafluoro-4,4'-biphenyldicarboxylic acid, were shown to be significantly more Lewis acidic than nonsubstituted UiO-66 and UiO-67 as well as the nitrated MOFs Zr-6-BDC-NO2 and Zr-6-BPDC-(NO2)(2). Zr-6-fBDC was shown to be a highly active single-site solid Lewis acid catalyst for Diels- Alder and arene C-H iodination reactions. Thus, this work establishes the important role of ligand perfluorination in enhancing MOF Lewis acidity and the potential of designing highly Lewis acidic MOFs for fine chemical synthesis.
Conjugated crosslinks boost the conductivity and stability of a single crystalline metal–organic framework
作者:Hua-Qun Zhou、Yonghe He、Jie-Ying Hu、Lai-Hon Chung、Qinfen Gu、Wei-Ming Liao、Matthias Zeller、Zhengtao Xu、Jun He
DOI:10.1039/d0cc06765b
日期:——
× 10−5 S cm−1). Oxidative treatment with FeCl3 guests then coupled the thiophene units to form conjugated bridges as covalent crosslinks. The resulting hybrid of a metal–organic framework and conjugated polymer featured robust crystalline order that withstood long-term air exposure and broad pH (from 0 to 12) conditions. Moreover, the homocoupled thiophene units, conjugated through sulfide links (–S–)
用Zr(IV)离子使具有四个侧基噻吩功能的连接分子结晶,以形成半导体多孔配位固体(1.1×10 -5 S cm -1)。然后用FeCl 3客体进行氧化处理,将噻吩单元偶联,形成共价桥作为共价交联键。由此产生的金属-有机骨架与共轭聚合物的杂化物具有坚固的结晶顺序,可以经受长期的空气暴露和宽广的pH值(0至12)条件。此外,通过硫键(–S–)与连接体主链共轭的噻吩单元均偶联,可提供更高的电子电导率(例如,> 2.2×10 -3 S cm -1),这是聚噻吩和聚苯硫醚的导电聚合物原型的特征。交联的固体还显示出在H 2 SO 4处理时可以广泛增加的质子传导性(例如,从5.0×10 -7增加到1.6×10 -3 S cm -1)。
Reactions and thermal decomposition of organolithium compounds derived from 4,4′-dibromooctafluorobiphenyl
作者:R.A. Contigiani、Hector E. Bertorello、M.Martinez de Bertorello
DOI:10.1016/s0022-328x(00)80154-0
日期:1971.10
is described. It is proposed that thermaldecomposition of the lithiated products formed at low temperatures (−80° to −90°) leads to products originating principally by nucleophilic displacement reactions, while rapid thermaldecomposition, after metal-halogen interconversion at temperatures of 0°, leads principally to products originating by elimination reactions. The intermediacy of benzyne species